Treatment of Synthetic Warp Sizes
In Activated Sludge Systems
CARL E. BRYAN, Research Associate
PEGGY S. HARRISON, Research Technician
Department of Textile Chemistry
North Carolina State university
Raleigh, North Carolina 27607
INTRODUCTION
The warp size used in the largest amount by far in the textile industry is starch and,
since it must be removed (scoured) from a fabric before dyeing, it contributes heavily to the
biochemical oxygen demand (BOD) of textile wastewater. I n recent years certain synthetic
polymers have been introduced for use as warp sizes; of these materials, polyvinyl alcohol
(PVA) and carboxymethyl cellulose (CMC) have gained the widest use. Although the cost
of these materials is higher than that of starch, they have certain advantages in performance,
particularly with yarns of the synthetics and cotton-synthetic blends, which tend to offset
this cost differential.
Besides giving increased operating efficiencies, the synthetic warp sizes, having a low
five-day BOD, have been promoted also as a means of reducing the water-pollution
potential of desizing wastes (1,2). Pronouncements from the Environmental Protection
Agency and the recently passed Water Pollution Control Act of 1972 now indicate that
BOD5 is becoming inadequate as a measure of organic pollution. Instead, the more
stringent measure of chemical oxygen demand (COD) or total organic carbon (TOC) may
be required.
We have taken two approaches to the problem of textile-desizing wastewater. In one
approach we have worked on the development of processes for recovering and reusing the
synthetic sizes from desizing wastewater; in the other we have studied the fate of these sizes
in biological treatment systems (3). The results obtained in the latter are the subject of this
paper.
BACKGROUND
When this study was begun, in 1970, there was no material in the literature on the fate
of PVA and CMC in biological waste-treatment systems. Because these materials, as well as
other synthetic polymers proposed as warp sizes, possess a low BOD, it was assumed
apparently that they pass unchanged through the treatment systems or are removed,
partially at least, by adsorption on the biological mass.
Several papers had appeared on the biodegradation of CMC under laboratory
conditions. Freeman, Baillie and Macinnes (4) found that solutions of CMC underwent a
loss in viscosity upon standing at room temperature for 32 days in the absence of a
bacteriostat. They isolated gram-negative bacteria which grew rapidly in media containing
CMC as the only carbon source, with a resultant loss of viscosity. In a study of the susceptibility of cellulose derivatives to attack by a fungus, Siu, Darby, Burkholder and Barg-
hoorn (5) found that CMC of low degree of substitution (DS) was metabolized. Using a
number of strains of fungi and bacteria, Reese, Siu, and Levinson(6)found that the growth
of most microorganisms was very good on CMC preparations of low DS. When the DS was
bove 1.0. however, growth was slight. Accelerated enzymic degradation studies by Wyrick
(7) of a series of six CMC's varying in DS from 0.41 to 2.45 showed that stability improves
with increasing substitution, the sample with DS 2.45 being essentially refractory to enzyme
attack.
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